Heart rot trees, a common and incurable fungal disease, have a surprising impact on the environment. These trees, found in upland forests, are emitting more methane than they absorb, challenging our understanding of carbon models. This discovery could significantly affect our knowledge of climate regulation and the role of forests in carbon sequestration.
Methane, a potent greenhouse gas, is over 30 times more effective at trapping heat than carbon dioxide. Healthy forests typically act as methane sinks, absorbing more methane than they release. However, the presence of heart rot disease in trees can disrupt this balance. The research, conducted at the University of Notre Dame Environmental Research Center, reveals that diseased trees emit more methane, potentially turning them into methane sources.
The study, published in the journal New Phytologist, employed sonic tomography to measure the severity of heart rot non-invasively. This technique uses sound waves to map the rot inside tree trunks, showing that methane emissions increase with the severity of the disease. Interestingly, carbon dioxide venting remained stable regardless of disease state, but methane emissions were higher in diseased trees.
The researchers also found that methane emissions originated from the heartwood, the central part of the trunk, while carbon dioxide peaked just beneath the bark. This discovery challenges the previous assumption that methane was primarily absorbed through the soil.
Further analysis revealed that methanogens, single-celled microorganisms, play a crucial role in methane production. These methanogens break down heartwood, aided by heart-rot fungi, but the fungi themselves do not directly produce methane. The presence of methanogens was confirmed through genomic sequencing of wood samples from the heart of each tree.
As heart rot progresses, it creates an ideal environment for methanogens to thrive, leading to increased methane emissions. Bark fractures, caused by the deterioration of the tree's interior, further facilitate the release of methane from the heartwood to the exterior. This process creates 'hot spots' of methane emissions on the tree's surface.
The implications of this research are significant. It suggests that ecosystem models may have overestimated the amount of methane absorbed by upland forests. The study also highlights the complex relationship between heart rot, methanogens, and methane emissions, emphasizing the need for further investigation into the carbon cycle and the impact of forest diseases on climate regulation.
The University of Notre Dame Environmental Research Center is well-positioned to continue this cutting-edge research, integrating genomic analysis with ecosystem gas flux studies. The center's natural setting and scientific infrastructure provide an ideal environment for exploring the mysteries of methane sources and sinks in forests.
